The present invention relates to mechanically strong, water-disintegrable agglomerates containing various particulate calcium sources for use as a soil conditioner to neutralize soil acidity and provide a source of nutrient values. The present invention also relates to processes for forming such agglomerates.
Soil conditioners or liming agents are widely used in agriculture, lawn care and gardening to reduce soil acidity and promote plant health. A variety of calcium-containing materials, in particulate or granulated form, are used as soil liming agents. Conventional liming agents include: limestone (CaCO.sub.3), dolomitic limestone (CaOMgO.2CO.sub.2), lime (CaO), slaked or hydrated lime (Ca(OH).sub.2), and gypsum (CaSO.sub.4.2H.sub.2 O).
Many industrial processes produce waste solids containing calcium. For example, the manufacture of cement and lime is accompanied by the generation of large quantities of dust collected from the hot gaseous effluents vented from the kiln. Similar calcium-containing dusts are recovered from the stack gases and ash residues produced during the burning of manure fuels (i.e., manure ash). These particulate wastes share two properties that make them potentially useful for application to cultivated soils: (1) significant acid neutralization capacity; and (2) high concentrations of calcium and other important soil nutrients such as potassium and sulfur.
Although some have suggested liming soils with cement kiln dust (See T. A. Davis, et al., "Disposal and Utilization of Waste Kiln Dust From Cement Industry", EPA Report No. 670/2-75-043 (May 1975)) as a way of reclaiming this sizeable waste stream, one serious hindrance to expanded agricultural use cement kiln dust and similar waste products are the problems associated with storage, handling and application of these finely divided materials to soils.
Raw cement kiln dust, for example, is extremely fine, typically consisting of particles having an average particle size much less than 100 .mu.m, with a large portion of particles often having a particle size of 10 .mu.m or less. As a result, the dust is easily carried away by the wind and is difficult to bulk-blend with other materials in preparing various fertilizer formulations. Furthermore, modern fertilizer application equipment for broadcast or row placement of solid fertilizers, is designed for handling free-flowing, granular or pelletized materials having an appreciable mean diameter, not dust. Consequently, numerous problems are encountered when such equipment is employed for field application of finely-divided dust.
Accordingly, it would be highly beneficial to develop a process for granulating or agglomerating cement kiln dust and other calcium-containing materials capable of consistently producing a mechanically strong soil conditioning agglomerate that readily disintegrates when contacted with water.